Re: CAJ/JCA question

["J. Lewis Muir" <jlmuir@imca-cat.org>]

On 6/14/13 3:45 PM, Till Straumann wrote:
> My 2 cents:
> 
> I advise against setting this (or any) property from code.
> This might surprise and/or frustrate users who *do* want
> to use property files etc.
> 
> You can set 'jca.use_env' from a file or even on the command line
> 
> java -Djca.use_env=true
> 
> Cheers
> - Till

Hi, Till.

I think it depends on the situation.  If you're deploying a program or
library for someone to use, I think it's fine to set the property in
code if you've decided that's how the program or library behaves--it
take CA configuration from the environment.

In Mark's example, I think it also makes sense because he's deploying a
plug-in for ImageJ.  Plenty of people will start ImageJ by simply
double-clicking an application icon for it; they're not starting it by
typing "java" and arguments at a command prompt.  And again, he's
effectively defining how the plug-in receives its CA configuration--from
the environment, not from a properties file.  He could put the
properties file in the areaDetector plug-in JAR file, but what use is
that?  No one is going to extract it, change the properties file, and
create the JAR file again.  That's a pain, and now you've also modified
the JAR in a site specific way.

Where a properties file could be useful is for a library where its
environment might be harder to control (e.g. in a Servlet running in
Tomcat).

Or it could be useful just for the case you're talking about where a
user wishes to be able to control it with a properties file.  But that's
up to the author of the application or library to decide how they want
to allow it to be configured.

Lewis